ARP question

[Robin Laing]

Tim wrote:
> On Thu, 2007-06-21 at 04:17 -0500, Rick Sewill wrote:
>> In the case of the cable companies, I believe they treat the cable like
>> it is a broadcast interface.  I believe they ARP for that IP address to
>> get the MAC address for that machine.  I get these ARP requests because
>> they are broadcast to me and to everyone with whom I share the cable. 
> 
> Yes, but it tends to be a group of people on one cable (perhaps everyone
> on one street, or a few streets), not every customer for the ISP is in
> that group.  *Part* of the path between you and the ISP is shared, you
> don't all have an individual, isolated, connections.
> 

I was on Cable for a few years and I was a good friend with that old 
system manager.  Cable companies only segment when they need to and when 
demand pushes it.  Our local cable company had two segments for the 
whole city.  ~8,000 customers.

It was related to cost and the need to supply reliable service.  He 
wanted to segment further but it would have required a major change and 
management wouldn't go for it.  Needless, he left soon after because he 
knew it was going to become a major headache.

At the time, there was no port blocking on the cable routers so opening 
up a network browser found a large amount of shared computers available 
on the network.  What fun someone could have had.  :)

When I moved to DSL from cable, I was shocked at how the speed differed 
between the two during the heavy evening usage.  I could access the 
cable companies local servers faster through DSL than with the Cable 
modem.  Ouch.


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Robin Laing